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Foam still a key concern for shuttle launch

The loss of foam is once again a key concern in the run-up to the launch of the next space shuttle, NASA officials said on Friday.

The shuttle Atlantis is tentatively set to lift off on 27 August, but programme managers will meet on Tuesday and Wednesday to officially determine whether it is fit to fly.

That meeting is likely to spark the same debates about foam as did the previous Flight Readiness Review, which occurred before the flight of the shuttle Discovery in July, says shuttle programme manager Wayne Hale.

During Discovery’s Flight Readiness Review in June, NASA’s chief engineer and chief safety officer withheld their full approval until one specific part of the tank, which could release foam, was redesigned (see NASA sets shuttle launch date despite objections).

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“I wanted to start off by reminding you that in this next flight, we do expect to have some foam loss from the tank,” Hale told reporters on Friday.

Normal wear and tear

Indeed, despite attempts to minimise the loss of foam on the most recent Discovery mission, Hale said the external fuel tank lost no less foam than usual. The orbiter also experienced an average number of “dings” to its heat shield.

But many had originally thought the successful shuttle flight was one of the cleanest on record, with few dings. Even the astronauts thought so after walking underneath the orbiter just after it landed on 17 July.

But a closer inspection revealed the mission was just average in terms of foam losses and impacts to the heat shield. “Beware of first reports, that’s my motto,” says Hale.

NASA has been struggling to reduce the orange foam that falls off the external tank, which holds the liquid fuel for the shuttle’s main engines, ever since the Columbia disaster in February 2003.

Titanium cover

A 0.73-kilogram (1.6-pound) chunk of foam fell off Columbia’s external tank and struck the wing, leaving a gaping hole that destroyed the orbiter on re-entry through the atmosphere.

NASA subsequently redesigned parts of the tank to reduce the foam losses. But there are still areas that NASA wants to revamp, including foam wedges called ice/frost ramps.

These ramps cover metal brackets that hold fluid lines onto the outside of the tank. They prevent the brackets from developing ice and frost that could also fall off the tank and damage the orbiter.

In late September, NASA will test two redesigned ice/frost ramps in wind tunnels. The more promising of the two is a titanium housing that would go over the brackets instead of foam. Hale says the agency expects to have a solution ready for launch by February or March 2007.

Atlantis’s six crew members underwent a dress rehearsal of the launch countdown on Thursday.